A cylinder-head gasket is compressed between the cylinder head and engine block of an internal-combustion engine to prevent leaks at this joint. Normally such a cylinder head is made of a compressed mass of heat-resistant material such as asbestos. Holes are formed in this sheet of asbestos material for the passage of liquid and oil in the motor block as well as for the cylinders which must pass through the gasket.
In order to prevent leakage at the critical region around the edges of the cylinder holes it is known to provide such a gasket at its cylinder holes with rings of reinforcement material. These rings are of outwardly open U-section and are gripped over the edges of the cylinder holes. They greatly increase the resistance of the gasket to rupture.
Normally such a reinforced gasket is relatively effective. It is clamped between the longitudinally extending cylinder head and engine block by bolts normally provided around the periphery of these two elements. As a result of this style of clamping the gasket head and the way in which the engine block and cylinder head normally deform when heated and under pressure, the most common accident is for the cylinder gasket to blow out between adjacent cylinders. Such a blowout reduces pressure in the two cylinders that are thus interconnected and requires a costly overhaul of the engine.
The only solution proposed to this problem has been to yet again reinforce the rings by making them substantially thicker. The result has not, however, been a substantial decrease in the number of blowouts between adjacent cylinder holes. Although a thicker reinforcement ring does generally prevent damage at the cylinder holes, the blowout between adjacent cylinder holes is still the most frequent accident.